Risk-Based Inspection Technique - Offshore Structures: Design, Construction and Maintenance - page 580

TABLE 8.9 Grouted Piles

Non-Grouted Piles

Year Designed

< 1975 ≥ 1975

10 4

Score = tabulated score × weight

improvement. Similarly, the North Sea factor was included since platforms in
this region tend to have better joint design and therefore grouting will have
less of an impact.
It is worth mentioning that grouted piles will increase the structure s

strength, as discussed in Chapter 7 , so they will reduce the likelihood of failure.
If the piles are grouted, they are ignored in scoring an increased the likeli-
hood of failure.
As presented in Table 8.9 , the score for non-grouted piles is dependent on the
year of design of the platform. From a practical point of view, this score can be
reduced by around 60% if the platform is located in the North Sea, as joint design
there tends to have been much better than in other areas of the world, and therefore
grouting would have a much lower effect, as discussed in Chapter 7 .
As evident from Table 8.9 for this factor, grouted piles will interact with the
year designed and location. A weight factor has been added to reduce the effect
considerably in the North Sea, where platform joints have historically been
better designed.

'

Damaged, Missing and Cut Members
In the initial risk-based underwater inspection (RBUI) calibration work done in
1997, the change in the failure probability was estimated primarily using results
from the Joint Industry Projects and Puskart et al. (1994) relating the RSR to the
failure probability for a number of locations world-wide. The calculation of the
likelihood requires collecting numerous data about the platform

s configuration
and its current condition to assign risk. A key component is the number of
damaged members, as they can have a significant impact on the strength of
the platform.
The AIM Phase III project, undertaken in 1988, evaluated a platform with
numerous postulated damaged conditions, including several scenarios of
damaged members, ranging from 1 to 3 or more. The damaged members were
located at different regions of the jacket, including the waterline, mid-depth
and near the seabed. The results indicated that overall platform capacity was
reduced little with one damaged member, but that numerous damaged members,

'